Studies of retrograde changes in axotomized motoneurons have revealed fundamental changes in morphology, metabolism and physiology of these cells. Restructuring of the granular endoplasmic reticulum, s.c. chromatolysis, seems to be the basis for increased and modified protein synthesis. While cytoskeletal proteins with the exception of the neurofilament triplet go up, enzymes and receptors related to neurotransmission go down and new growth associated proteins appear. There is an enhanced glucose uptake and iron metabolism. Complex changes in axonal transport have been observed. This may reflect the efforts of the regenerating nerve cell to compensate for its lost axon.